The present disclosure relates to a pulsed laser device.
In the related art, pulsed laser devices of, so called, Master Oscillator Power Amplifier (MOPA) type that output high power pulsed laser light by amplifying a seed light source that outputs pulsed laser light as seed light with an optical amplifier, such as an optical fiber amplifier, have been disclosed (refer to Japanese Laid-Open Patent Publication No. 2002-118315). This type of pulsed laser device is used for laser processing or the like.
On the other hand, a technique of enhancing the extinction ratio in pulsed laser devices has been disclosed. The extinction ratio refers to a ratio of a power of light that is output when output of optical pulse is ON state to a power of light that is output when the output of optical pulse is OFF state. For example, Japanese Patent No. 4232130 discloses that optical pulse with high extinction ratio can be easily obtained by oscillating optical pulse having a pulse width of the order of 10 to 20 ns by current control of a DFB semiconductor laser, and by temporally extracting only a part of the optical pulse by an optical modulator, such as an Acousto-Optic Modulator (AOM), to modulate into an optical pulse having a pulse width of 1 ns. Moreover, Japanese Laid-Open Patent Publication No. 2010-192651 discloses that the extinction ratio can be enhanced by using an Electro-Optic Modulator (EOM) as the optical modulator, and by combining with a ring path constituted of a 2×2 optical switch to make light pass through the EOM twice. Furthermore, Japanese Laid-Open Patent Publication No. 2013-205556 discloses that the extinction ratio can be enhanced by combining a CW laser light source with the AOM and the EOM to generate an optical pulse. Furthermore, reference is made to U.S. Pat. No. 6,590,924.